Artificial blocks for the protection of hydraulic structures



P. F- DANEL July 9, 1963 ARTIFICIAL BLOCKS FOR THE PROTECTION OF HYDRAULIC STRUCTURES Filed Jan. 18, 1960 4 Sheets-Sheet l INV EN TOR PIERRE FRANCO/S DANEL *JZ/"WL ATTORNEYS July 9, 1963 P. F. DANEL 3,096,521

ARTIFICIAL BLOCKS FOR THE PROTECTION OF HYDRAULIC STRUCTURES Filed Jan. 18. 1960 4 Sheets-Sheet 2 INVENTOR PIERRE FRANCO/6' DANEL BY gm jp ww ATTORNEYS July 9, 1963 P. DANEL 3,096,521

ARTIFICIAL BLOCKS FOR THE PROTECTION OF HYDRAULIC STRUCTURES Filed Jam 18, 1960 I 4 Sheets-Sheet :5

'0 0 0 m 0 o o INVENTOR PIERRE FRANCO/5 DANEL P. F. DANEL July 9, 1963 ARTIFICIAL BLOCKS FOR THE PROTECTION OF HYDRAULIC STRUCTURES Filed Jan. 18, 1960 4 Sheets-Sheet 4 INVENTOR PIERRE FRANCO/S DA/VEL United States Patent ARTIFICIAL BLGCKS FOR THE PROTECTHON F HYDRAULIC STRUCTURES Pierre Francois Danel, La Tranche, France, assig'nor to Societe Grcnohloise dEtudes et dApplications Hydrauliq'nes, Grenoble,France, a corporation of France Filed Jan. 18, 1960, Ser. No. 3,196

Claims priority, application France 32:11.20, 1959 Claims. (Cl. 61-4) The present invention relates to artificial blocks for use in the construction of hydraulic structures, and more particularly to the type of artificial block which is employed in the protection of the embankments of marrtime breakwaters and jetties that are exposed to waves and wave action.

-An object of the invention is to provide improved blocks of the indicated type which when laid as a single layer on such an embankment, will provide a protective [facing therefore capable of withstanding the forces exerted thereon by the strongest waves that such embankment may be subjected to and which will not tend to be washed out of such layer, or of even being displaced from such layer, by hydraulic pressures from within the embankment.

Another object of the invention is to provide an improved block of the indicated type which has such excellent wave energy dissipation properties that a protective coating formed therefrom will result in substantial reduction of overtopping of the protected embankment by waves, thereby making it possible to reduce the size of a breakwater or jetty without loss in the efficiency thereof, and will reduce wave reflection to such a degree that substantially improved navigation conditions will exist near the structure.

A further object of the invention is to provide an im proved block of the indicated type which without chang ing its external dimensions may be modified in certain other structural features thereof to alter the characteristics of the block, such as weight, wave energy dissipation properties, permeability, etc., in a manner best suited for the particular conditions of its use and which will provide the optimum strength and efliciency qualities for that portion of the particular structure which the block is'to protect.

In forming a protective facing layer on the embankment of a wave defense structure with the blocks of this invention, it is preferred that the protective facing of the embankment be constructed by placing the blocks side by side so as to form a sort of even pavement of such blocks. The blocks may have any desired overall external appearance which is considered most suitable for the conditions of use thereof. Thus, the blocks may be prismatic externally, or have a generally square, hexagonal 'oi' cylindrical form. In certain cases, especially on those parts of the hydraulic structure Where the facing is curved, the blocks of the invention may be given the overall ex .ternal appearances of truncated pyramids.

The blocks of the invention are characterised in that they are provided with at least one large hole which may be in the form of a recess and opens toward the top thereof, and one or more openings or orifices afiording communication between the underside of the block and the uppersi-dethereof and which may extend from the top surface of the block and/ or the bottom of such hole to the bottom of the'block, both the hole or holes and the openings or orifices having cross-sectional areas that have been carefully designed to provide the block with the qualities desired. Generally speaking, the hole which governs the wave energy dissipation properties of the block should be as large as possible without detracting from the mechanical strength of the block and without reducing the "ice weight of the block below that considered sufficient to resist any hydraulic stresses acting on the block from within the structure. The said openings or orifices control the permeability of the block and the size and the number of such orifices and the total cross-sectional area thereof are determined by the size of the material in the hydraulic structure immediately below the blocks and the pressure dilference existing when water is caused to flow upwardly from the hydraulic structure and through such orifice or orifices. Thus, the size of the orifice or orifices should not be great enough to permit the underlying material of the hydraulic structure to pass therethrough. On the other hand, the total cross-sectional area of the orifice or orifices should be large enough to assure that the outward thrust on the block due to the water pressure against the bottom of the block is always less than the weight of the block.

The external overall dimensions of a block constructed in accordance with the invention, the proportion of void in such block and the dimensions of the hole and of the bottom orifice or orifices forming such void, all depend on the characteristics of the waves to which the hydrau lic structure of which such block forms a part is exposed, the position of the block on such structure, and the types of materials used to construct the core of such structure and their distribution within the structure. Dependent upon the conditions of use of the block, the total volume of the hole and orifices therein may constitute from. 20 to 60% of the volume of the whole block. Generally speaking, the variation of void volume in the blocks forming a protective facing for a hydraulic structure should be such that the hydraulic thrust against such facing is suitably distributed throughout the entire area of the facing and not permitted to become unduly concentrated in the blocks of localized portions of the facing. In practice, the blocks should be very permeable to Water as compared with the underlying core material of the hydraulic structure.

It is of particular advantage that the block of this invention may be readily modified in relation to its weight, to the volume of the hole, and to the dimensions of the bottom orifice or orifices, without altering the external shape of the block. Thus, blocks made in accordance with the invention and having identical external dimensions and shape may be laid as a coursed layer to form a facing of substantially uniform external appearance, but having at certain places thereof substantially different qualities which are especially suited to the hydraulic conditions existent in the underlying portions of the hydraulic structure.

On those parts of the hydraulic structure that are directly exposed to the impact of breaking waves, the weight of the blocks can be increased by reducing the dimensions of the holes thereof. In a facing embodying such blocks of greater weight and consequently of lesser permeability, the great permeability of the adjacent parts of the facing are relied upon to drain the underlying rocks forming the core of the structure and thus prevent the creation of dangerous pressures under such less permeable blocks.

The upper sloping part of the hydraulic structure can be protected advantageously'by providing in the portion of the facing layer overlying the same, blocks having a large hole capable of holding a large quantity of water so that when a large wave breaks on such blocks they tend to prevent overtopping of the hydraulic structure by such wave. In such a construction, the bottom orifices of the blocks should be so designed that when the Wave falls back, the holes of the blocks will be drained and the blocks emptied of Water in slightly less time than the length of the period of the most dangerous waves, i.e. very high Waves with long periods.

The blocks located on the lower sloping part of the hydraulic structure that is to be protected should have a smaller hole than those blocks on the upper sloping part of such structure to make them heavier than the latter. The blocks on such lower part of the structure should also have more and/or larger bottom orifices to enable them to drain away the water flowing from the upper blocks and through the underlying rocks forming the core of the structure. In determining the construction of these lower blocks, allowance should be made for the fact that when a wave falls back, the holes in the blocks will be momentarily filled with the water flowing through the structure from the upper blocks and the weight of which will be added to that of the blocks themselves to resist any hydraulic pressures on the blocks from inside the structure.

As has been above indicated, the blocks of this invention may be constructed in a large variety of shapes. It has been found that blocks in the shape of a cube are the easiest to make and place in position in a coursed layer on a hydraulic structure. Blocks with triangular and hexagonal cross-sections are also very easy to use in the construction of such a facing layer. The edges of blocks having these shapes may be chamfered or rounded off to improve the resistance of such blocks to deterioration. This treatment of the block edges provides a further distinct advantage in that when the blocks are laid as a pavement to form a protective facing on a hydraulic structure, interstices will be formed between the blocks making up such pavement and will improve the permeability of the facing to water. In designing the block to provide this advantageous feature, it is sufficient if the edges of the blocks are so formed that the cross-sections of the resulting interstices in the pavement are of the same order of magnitude as those of the bottom orifices in the blocks.

It has also been found to be of advantage in certain circumstances to vary the heights of the blocks in a manner dependent upon the positions they are to occupy in the facing layer. For example, blocks situated on the crest of the structure could be made higher so as to appreciably increase their water retaining capacity and thus diminish the likelihood of overtopping of the structure by waves. This increase in the height of the crest blocks maybe substantial and as much as to make them one-third higher than the blocks lower down in the facing layers.

It is believed that it will be evident from the foregoing, that the flow of water through a facing formed of blocks of this invention depends not only on the motion of the waves, but also on the permeability of the underlying rocks forming the core of the hydraulic structure protected by such facing. Accordingly, when constructing a core for such blocks, it is advantageous to use in the construction of such core rocks which will provide the correct permeability characteristics for each part of the cross-section of the hydraulic structure. In order to determine what these permeability characteristics should be in a particular structure tests may be made on a scale model of the type that is commonly made to determine the shape and characteristics of such maritime structures. In determining the permeability characteristics of the structure it is advisable also to allow a rather large safety margin to take care of possible settling and concretion of the structure.

It will be appreciated that the blocks of this invention, in order to enable them to exercise their intended control of the tremendous forces of the sea, are of semi-massive form and may range in weight from three to forty tons and even more. When such blocks are laid as a coursed pavement to form a protective facing layer for the maritime structure, their upper recessed ends will present to the advancing waves of the sea a cellular structure which has been found to be very effective in dissipating the energy of an oncoming wave. Tests have shown that such a construction, in addition to providing a high degree of hydraulic roughness, creates an air condition which is especially efiective to still further dissipate the Wave energy. When a wave breaks, a sheet of water covers the holes in the blocks which, particularly in the upper part of the structure, were emptied of water when the previous wave fell back. The sheet of water therefore, traps the air in the emptied holes and such air as it escapes outwardly from the holes causes in the sheet of water a boiling action which has a wave damping effect similar to that produced by compressed air breakwaters.

Because of the effective damping action exercised on the waves by the blocks, the amount of overtopping of the maritime structure by the Waves is reduced and this makes it possible to reduce the height of such structure. In certain cases it may be advantageous to make the structure wider, but not so high, and to cover the top of such structure with blocks having large holes capable of absorbing any water that begins to overtop the said structure.

The fact that the blocks of this invention depend for their effectiveness upon voids formed interiorly thereof and preferably have the configuration of a solid block without projections, renders them exceptionally sturdy despite their relative lightness for their size. The blocks may be made of any suitable material, but it is preferred that they be formed of molded concrete. When manufacturing the blocks it is advantageous to employ processes which are known to increase the mechanical strength of the concrete such as those involving vibration and vacuum. The stability of the block and of the structure in which it is employed are not endangered if the edgw of that part of the block in which is formed the hole are broken occasionally. Also accidental stopping up of a block is not dangerous as the pressure under the plugged block cannot rise too much on account of the permeability of the blocks which surround it.

When, instead of forming the blocks as a layer on the maritime structure, they are placed pell mell on the sloping parts of such structure, the blocks will assume a great variety of positions to provide spaces of widely varying sizes between them, thereby increasing the permeability of the facing formed thereby. The obvious advantage of placing the blocks in this pell mell fashion is that it is the easiest way to lay them. This disposition can be used, for example, for the protection of embankments exposed to Waves with medium period or for repairing partially destroyed structures.

The features of the blocks of the invention and their advantages are described in greater detail in the following description which should be read with reference to the accompanying drawings in which are illustrated by way of example different forms and uses of the blocks and in which:

FIG. 1 is a vertical sectional view of a block embodying the essential features of the invention;

FIG. 1a is a view similar to FIG. 1 showing a different arrangement of the hole and orifice thereof;

FIG. 2 is a top plan view of the block shown in FIG. 1;

FIG. 3 is a vertical sectional view of another form of 'block embodying the invention;

FIG. 4 is a top plan view of the block shown in FIG. 3;

FIG. 5 is a vertical sectional view of another embodiment of the invention;

FIG. 6 is a top plan view of the block shown in FIG. 5;

FIG. 7 is a vertical sectional view of still another embodiment of the invention;

FIG. 8 is a top plan view of the block shown in FIG. 7;

FIG. 9 is a vertical cross-sectional view of a breakwater provided on its seaward slope with a protective facing of blocks made in accordance with the invention;

FIG. 10 is a view similar to that of FIG. 9 and showing another form of breakwater embodying the invention;

FIG. 11 is a partial plan view of a breakwater head protected by 'a facing of blocks embodying the invention;

FIG. 12 is a perspective view of a special type of block embodying the invention;

FIG. 13 is a perspective view of an alternative design of the type of block shown in FIG. 12;

FIG. 14 is a partial plan view of a facing composed of blocks similar to that shown in FIG. 13; and

FIG. 15 is a top plan view ofa part of a break water and illustrates another manner in which the blocks of the invention may be laid to form a protective facing therefor.

Referring now more particularly to FIGS. 1 and 2 of the drawings, the block shown thereby has a cubic form and is provided with a hole 11 in the form of a recess and which extends from the top of the block to a depth of more than two-thirds of the height of the block. The hole 11 is substantially square in horizontal section and forms the major portion of the volume of the block in the region occupied thereby so that such recess is enclosed by a side wall of square configuration in cross-section. As indicated, this wall may be tapered on its inner sides. Opening into the bottom or inner surface 12 of the hole 11 is a circular opening or orifice 13 which extends downwardly toward the bottom of the block and communicates at its lower end with a cavity formed in the bottom face 14 of the block. The cavity 15 which forms an end enlargement of orifice 13, is substantially larger in crosssection than the main portion of orifice 13 and enables the block to receive portions of and thereby to become interlocked with the rocks of the core of the hydraulic structure on which it is laid. This cavity 15, however, should be rather shallow so as not to afiord space into which such rocks may be forced by the hydraulic forces present in the core with consequent deterioration of the core structure.

As has been indicated the primary purpose of the hole 11 is to dissipate the energy of the waves breaking on the maritime structure and it accomplishes such purpose in the manner previously described. The hole 11 also coacts with the opening or orifice 13 to provide the permeableness required in the block under its particular conditions of use, as has also been previously pointed out. The previous discussion further indicated that the volume of the hole 11 and the diameter of the orifice 13 for a given block are carefully determined with due consideration to the requirements for such block in its use, including factors relating to the position of the block on the maritime structure, the permeability of the core of such structure, the size of the waves likely to be encountered, etc. In the block illustrated in FIGS. 1 and 2 of the drawings, the voids formed by the hole 11, orifice 13 and cavity 15 make up approximately 27% of the total volume of the block 10. In this connection, the relation between the area of the top of the block and cross-sectional area of the hole 11 thereof is critical in the sense of accomplishing satisfactory substantial wave energy dissipation effects under actual conditions of use without substantial detraction of other qualtiites of the block desired for such use. Thus, it is estimated that the cross-sectional area of the hole 11 at theto-p of the block should be within the critical range of from 15 to 60% of the area of the top of the block in order to obtain such results. As an example of a block conforming to this critical range, a cubic block of 3 meters side dimension and for which the relation between the area of the top of the block and the cross-sectional area of the upper end of the hole 11 thereof is selected to be 60%, would have a wall thickness at the top of 35 centimeters. A pavement formed of such blocks would be very eifective as a wave destroying means and yet would have suflicient structural strength to successfully withstand the conditions of its use.

As has been previously indicated, it is within the contemplation of the invention to make theorifice 13 separate from the hole 11 instead of in communication therewith in order to provide the block with the desired permeableness. Thus, as is shown in FIG. 1a of the drawings, the orifice 13' of the block 10' is separate from the hole 11 and extends from the lowerside of such block to the top side thereof.

FIGURES 3 and 4 of the drawings also show a block of cubic form but of simpler construction than the block of FIGS. 1 and 2. In the block 30 of FIGS. 3 and 4, the bottom orifice 33 has been formed as an extension of the hole 31, which has no bottom, so that the combined hole and bottom orifice form a continuous passageway through the block. However, the hole portion 31 and bottom orifice 3-3 of such passageway function in a manner similar to the hole 11 and orifice 13, respectively, of the previously described block 10 to produce substantially the same results in the protective facing of which such block forms a part. The volume of the hollow part of the block of FIGS. *3 and 4 is approximately 25% of the total volume of the block which ratio is slightly less than the void ratio in the block of FIGS. 1 and 2. Block 30 may he pro vided also with a cavity in its bottom face similar to the cavity 115 of block 10 to improve its ability to adhere to the rocks forming the core of the maritime structure.

In the modified form of cubic block 50 shown in FIGS. 5 and 6 of the drawings, the hole 51 thereof is made in the form of a shallower recess than the recess 11 of block 10 and four orifices 53 extend from the bottom Wall 52 of such recess to the cavity 55 provided in the lower face 54 of such block. By providing four orifices 53 instead of one, as in the block 10, the drainage area in the bottom 52 of hole 51 is increased and the lower portion of the block below hole 51 is formed into a cellular structure which tends to increase the strength of the block. in the block of 'FIGS. 5 to 6, the combined volume of the cavities 51, 53 and 55 is approximately 30% of the total volume of the block. 7

The embodiment indicated in FIGS. 7 and 8 of the drawings, is essentially similar to the block 50 of FIGS. 5 and 6, in that it is provided with a large, somewhat shallow hole 71 which is in communication at its inner wall 72 with a plurality of orifices 73 that impart a cellular structure to the base of the block. Block 70 differs from block 50' in its external configuration which is such that a horizontal cross-section thereof is hexagonally shaped. This configuration of block lends itself more advantageously to random placement and diagonal coursing of the blocks in forming the protective facing for the maritime structure. Such configuration also has an advantageous effect on the strength of the block. Because of the configuration given block 70, the four orifices 73 thereof are arranged somewhat diiierently than the orifices 53 of block 50. The combined volume of such orifices 73 and of the hole 71 and the bottom cavity 75 is substantially similar to the volume of the void in block 50 in that it constitutes approximately 29% of the total volume of the block.

FIGURES 9 and 10 of the drawings illustrate two ex amples of rock filled breakwaters, the seaward slopes of which are protected by facings of coursed blocks embodying the invention and constructed so that their characteristics are suitably adapted to the varying permeability conditions to be found in dilferent parts of the rock filled core mounds or sections of the structures. In the breakwater depicted in FIG. 9, there is provided a central core of very low permeability. Core 90 may be formed of rock known as quarry run which will provide a volume of void constituting about 20% of the total volume of such core. In determining the permeability of such core it must be remembered that what is being referred to is the permeability of the core to the fiow of water so that in such determination as is known to those skilled in the art, there must be taken into consideration not only the void ratio of the material forming such core, but also other factors such as the shapes of the particles in the material defining such voids and of the flow paths formed by such particles. Thus, with a material such as quarry run which may be constituted of pieces of rock of all different sizes and a substantial portion of which may be in the form of dust, even though such material has a void ratio of about 20% its permeability to water is quite low.

The upper and middle parts of the seaward bank of the core may consist of a reasonably permeable mass of rocks 91, such as rocks of such range of sizes as will provide a 25% void ratio. The mas-s'of rocks forming the lower part 92 of the support for the protective facing should be very permeable and may be constituted of medium and large sized rocks such as will provide a void ratio of approximately 30%. The mound of rocks 93 at the toe of the breakwater should be as permeable as possible and preferably is formed of very large stones capable of providing a void ratio of as much as 40%. The rockfill cap 94 and the inshore bank 95 are also reasonably permeable. For example, the cap 94 and bank 95 may be formed of stones in approximately the same range of sizes used in the rock mass 92 to provide a void ratio of approximately 30%.

The blocks of the invention forming the protective facing on the seaward bank of the breakwater illustrated are laid in a coursed manner on the masses of rocks 91 and '92 and are located between the mound of rocks 93 at the toe of the breakwater and the cap of rocks 94 at the top of such structure. The blocks forming the lower part of such facing and designated 96, are provided with orifices 97 of large cross sectional area so as to make them very permeable to water. The blocks 98a and 93b located further up on the structure are provided with orifices 99 of smaller cross-sectional area than orifices 97 and such as to make these higher blocks of medium permeability.

The approximate relation of the permeabilities of the above indicated components of the breakwater structure illustrated in FIG. 9 may be as indicated in the following tabulation, wherein the letter P designates the permeability to water of the components and the numbers in parentheses are the reference characters designating such components in FIG. 9:

It is believed that the manner of cooperation of the several components of the breakwater structure shown in FIG. 9 of the drawings will be readily understood from the foregoing discussion. However, it may be pointed out here that when a wave breaks on the seaward bank of such structure, the energy thereof is substantially dissipated by the upper recessed portions of the blocks forming the protective facing and to such an extent that the wave is unlikely to over-top the structure or to produce a wave reflection that will seriously alfect navigation conditions near the structure. The water from the breaking wave will submerge the lower blocks 96 and fill the holes or recesses of the upper blocks 98a and 98b. The water in the upper blocks 98a and 98b will flow dovvn through the orifices 99 thereof and into section 91. As the wave retreats, the water in section 91 will drain out of the breakwater through the orifices 97 and the holes in the lower blocks 96.

In certain circumstances, it may be important to reduce the pressure applied by such water within the breakwater to the undersides of the lower blocks 96. To do this it is necessary that the amount of water flowing downwardly through the rockfill 91 and 92 be reduced. Such a result may be accomplished in the manner illustrated in FIG. of the drawings. In the breakwater shown in this figure, the core 100 and the rock filled sections 101, 102, 103 and 104 thereof are constructed to have permeabilities corresponding to the core 90, and sections 91, 92, 93 and 94, respectively, of the breakwater shown in FIG. 9 of the drawings. Also the blocks 106, 103a and 108b are substantially similar to blocks 96, 98a and 98b, respectively, in the breakwater of FIG. 9; the lower blocks 106 having relatively large orifices 107 and the upper blocks 108a and 108b having small orifices 109'. So far as the indieated sections of the breakwater of FIG. 10 and the blocks thereof are concerned, they will operate in a manner substantially similar to that described with relation to the corresponding parts of the breakwater of FIG. 9. The

core in the latter structure, however, and the reasonably permeable rockfill section 101 forming the upper part of the core mound are so constructed that the water trapped in the upper blocks 108a and 10% of the protective facing in major part flows to the inshore side of the breakwater. To prevent this inflowing stream from damaging the inshore bank of the breakwater, the rockfill section 101 is extended over the inshore slope of the core 100 to provide a reasonably permeable inshore extension 101a which is covered with a layer of rockfill a having low permeability. The rockfill layer 105a is in turn covered with a layer 105]) of rockfill which is reasonably permeable and extends down from the rockfill cap 104 as a cover facing for the inshore bank of the breakwater. The building up of the breakwater on the inshore side of the core in this manner prevents the generation of dangerous internal pressures which might damage the facing of the inshore bank of the breakwater.

It Will be observed that in some instances the seaward portion of a breakwater which is to be covered by a protective facing, is somewhat curved, such as at the part thereof between the seaward slope and the crest of the structure, and at the head of the breakwater. In such a situation, the blocks of the invention can be suitably tapered to provide a close fitting thereof between themselves and the other blocks in the facing. This advantage of the blocks of the invention is illustrated by the blocks 98b in FIG. 9 and by the blocks 1108b in FIG. 10 which seat on curved surface portions of the rockfill sections 91 and 101, respectively, and which have a vertical taper in the plane of the drawings. As to curvature in the head of the breakwater, FIG. 11 of the drawings shows in plan view a part of the facing on the slope of a breakwater head and illustrates how specially designed blocks 1181: taper in the plane of the drawing to take care of such curvature and are used in connection with ordinary right angularly shaped blocks 11801 of the type of blocks 96 and 106.

In other situations it is important to take particular care in the manner in which the blocks are coursed in a protective facing. Thus, it may be necessary under certain conditions to lock the blocks together after having been laid in the manner desired or to lay them in diagonal courses which may or may not be locked together. If the blocks are to be locked in their coursed positions, it is preferred that specially formed blocks of the type illustrated in FIGS. 12 and 13 be employed. The block of FIG. 12 is constructed in a manner substantially similar to the block 10 of FIGS. 1 and 2 in that it is provided with a large upper hole and a communicating orifice or orifices in the base portion thereof. Block 120 is additionally provided with grooves 121 in the outer surfaces of its side Walls and which extend from the top of the block to a point short of the bottom thereof to provide a bottom shoulder or end wall 122. It will be understood that when blocks 120 are coursed in the manner described, the grooves 121 thereof will become aligned with similar grooves on the opposed surfaces of adjacent blocks to form cylindrically shaped cells which are closed at their bottom ends. These cells are filled with a suitable cement to key the blocks together. It is preferred that the cement be a bituminous cement composed in major part (about 60%) of asphalt or bitumen and the remainder (40%) of sand and gravel. Such a cement behaves practically like a solid when subjected to shock stresses and prevents the blocks from moving under the forces created by wave action. However, when a force is applied to the blocks for a prolonged period, such as results when the protective facing is settling on the breakwater structure, the bitumen in the cement flows to permit the slow displacement of the blocks compelled by such settling action. The gravel in the bituminous cement slows up any tendency of the bitumen to flow and prevents it from leaking away from the blocks through the narrow openings therebetween.

In the form of block designated in FIG. 13 of the drawings, instead of forming grooves 121 in the side walls thereof as in the block of FIG. 12, such block 130 is formed with four corner bevel surfaces 131 which extend down from the top of the block to a point short of the bottom thereof to leave four triangularly shaped corner portions 132. at the bottom of the block; Thus, when blocks of the form of block 130 are laid in coursed rows to form a facing, as shown in FIG. 14 of the drawings, the bevel surfaces 131 and the bottom corner portions 132 which will be [located at the center of each four adjacent blocks 130, will form a cell having a closed bottom. In-to each of such cells is poured bituminous cement 140 to key the four blocks together in a manner substantially similar to that described with respect to the blocks 120.

FIG. 15- illustrates the manner in which the blocks of this invention maybe laid in diagonal courses. The blocks 159 in FIG. 15 are substantially similar in construction to the blocks of FIGS. 1 and 2 and are laid to form a facing for a breakwater which is substantially similar in construction to the breakwater shown in FIGS. 9 and 10 and which is provided with a rockfill toe mound 151 corresponding to the toe mounds 93 and 105 shown in FIGS. 9 and 10, respectively. In setting out the blocks 150 to form a facing with diagonal courses, the first row is suitably placed and packed against the rockfill toe mound 151. In laying the blocks in the subsequent rows, each block th: is placed in its approximate position and it will then automatically seat itself in its exact proper position by sliding down the adjacent face of a neighboring block 1501). It wili thus be seen that after the laying of the initial row, the placement of the following rows is facilitated by the diagonal arrangement.

While there has been hcreinabove described and illustrated in the drawings several preferred forms of the invention, it will be apparent to those skilled in the art that other designs and methods of application may be made within the contemplation of the invention. Thus, it is possible, for example, to combine four cubic blocks of the type previously described into one unitary block by constructing a mold therefone which will enable this to be done in one pouring operation. Such a block, having the same height as a single block, but having a seating area four times greater than the latter, would be substantially more stable than a single block. Further, without any sacrifice of the seating or covering area thereof, such a block could be substantially lightened in its weight since the partitions separating the four recesses therein could be made thinner.

It is also within t e contemplation of the invention to increase the surface roughness ofra facing produced by laying blocks of the invention in an even pavement, by providing such blocks at the upper edges thereof with one or more tooth-like extensions. For example, a cubic block .of the type of block 10 in FIG. 1 of the drawings, could be provided with one or more teeth, each tooth being situated at one corner of the biock in the manner of tooth 16. shown in FIGS. 1 and 2. A hexagonal block such as shown in FIGS. 7 and 8 of the drawings could have three teeth 76 situated at alternate top corners thereof. 1

It will be understood from the foregoing that it is not intended that the invention should be restricted to the disclosures herein, but that it is intended to include all forms of the invention coming within the scope of the appended'claims.

I claim:

1. A hydraulic structure for protection against the action of moving water and composed of a sloping embankment having a protecting facing provided on the water side of said embankment, said embankment comprising an inner mass of material of low void ratio and low permeability to the flow of water therethrough and having a supporting surface sloping down under the water, and said embankment having provided on such sloping surface a sloping layer of rocks of such sizes as to provide in such layer a void ratio substantially greater than the void ratio of said inner mass, and a greater permeability than said inner mass and such that water absorbed thereby from a wave thereof is enabled to flow down therethrough over said sloping surface at such rate that the absorbed water is substantially drained therefrom while such wave is receding and before a successive wave breaks 011 said structure, said facing being mounted on said sloping layer and being very permeable to the flow of water therethrough as compared with said sloping layer, said facing comprising a plurality of hollow boxshaped blocks laid as a layer on the lower portion of said sloping embankment layer and disposed generally in side-by-side relation with the outer side walls thereof in supporting engagement, each of said blocks being of large size and weight and having at least one large cavity enclosed by a vertically disposed wall in the upper portion of the block so as to present a large aperture to water impinging on the facing, and having at least one orifice in the bottom wall of the block bringing such large cavity into communication with the portion of the sloping layer on which it rests, the total volume of the cavities and orifices in said blocks constituting from 20% to 60% of the total block volume so that said blocks are relatively light in weight for their size and unable by their own Weight to withstand substantial hydrodynamic underpressur-es exerted against their bottom walls by water flowing down through said sloping embankment layer, the total cross-sectional area of the large cavities in said blocks being substantially greater than the total orifice cross-sectional area in the bottom walls of such blocks, and at the tops of the blocks, constituting from 15% to 60% of the total area of the facing formed by such blocks, so that the upper portions of the blocks are substantially lighter than the lower portions thereof and present to an incoming wave of water a cellular construction capable of destroying the formation thereof and of absorbing such a substantial portion of the water of such wave that formation of a major reflection of such wave would be prevented, and the orifices in said blocks being sufiiciently large as to enable water flowing down from the upper portion of the sloping embankment layer to drain out of such orifices and cavities at such rate as to prevent the outward hydrodynamic thrust on the bottom walls of said blocks from building up to a magnitude greater than the weight of the blocks.

2. A hydraulic structure such as defined in claim 1, in which said facing comprises a plurality of said hollow box-shaped blocks laid generally as a layer on a higher portion of said sloping embankment layer against which waves may break, the cavities in said blocks on such higher portion of the embankment occupying the major part of the area of the upper portions of the blocks with openings at the tops of the blocks constituting from 15% to 60% of the total area of the facing formed on such higher portion of said sloping embankment layer, and said cavities providing in each such higher block a cavity volume greater'than the volume of the cavity in each of the blocks on the lower portion of said sloping embankment layer and such'that said higher blocks present a cellular construction capable of destroying the formation of an advancing wave and of absorbing and storing such a substantial portion of the water thereof, that a major part of the water of the advancing wave is engulfed within said cavities and rendered unable to form a major reflection of such wave, and the orifices in said higher blocks being of such size as to enable the engulfed water to pass through such blocks at a rate such that the engulfed water can flow into and down through such higher portion of said sloping embankment layer so as to be drained from the latter before a successive wave breaks on said structure.

3. A hydraulic structure such as defined in claim 1, in which the cross-sectional areas of the orifices at the l 1 bottom Walls of said blocks are generally smaller than the cross-sectional areas of the rocks in said sloping embankment layer on which said hollow box-shaped blocks are seated.

4. A hydraulic structure such as defined in claim 1, in which said embankment comprises a toe portion abutting the lower end of said sloping rock layer, said too portion being constituted of rocks of large size providing it with a permeability to water flow substantially greater than that of said sloping rock layer and providing an abutting shoulder forming a support for the bottom rows of blocks mounted on the lower end of said sloping rock layer, said bottom rows of blocks being laid against the shoulder provided by said toe portion and being curved transversely to the direction of slope of said sloping rock layer so as to enclose the lower end of such sloping layer.

5. A hydraulic structure for protection against the action of moving water and composed of a rubble mound in the form of a sloping embankment and a protecting facing provided on said sloping embankment, the rubble in said embankment being of such sizes and configurations as to provide the embankment with such permeability that water absorbed thereby from a wave thereof is enabled to flow down therethrough while such wave is receding and to be substantially drained therefrom before a successive wave breaks on said structure, said facing comprising a plurality of container shaped blocks laid as a layer on the lower portion of the embankment and disposed generally in side-by-side relation with the side walls thereof in supporting engagement and the top faces thereof exposed to the movements of the water, each of said blocks being relatively massive and of substantial weight and having a large cavity opening in its top face and at least one orifice in its bottom face bringing such large cavity into communication with the portion of the embankment on which it rests, the cavity and orifice constituting from 20% to 60% of the total block volume and occupying such a large portion of the volume of the block that the block is relatively light in weight for its size and unable by its own weight to withstand substantial hydrodynamic underpressures exerted against its bottom face by water flowing through said embankment, the cavity in each block occupying the major part of the area of the upper portion of the block, whereby said layer of such blocks presents to an incoming wave of water a cellular construction which is capable of destroying the formation thereof and of absorbing and storing such a substantial portion of the water of such wave that formation of a major reflection of such wave would be prevented, and the orifices in said blocks being of such size as to enable water flowing down from the upper portion of the embankment to drain out through such orifices and cavities at such rate as to prevent the build up of hydrodynamic under-pressures to a magnitude suflicient to displace such blocks on the embankment, and said facing comprising a plurality of said container shaped blocks laid generally as a layer on a higher portion of the embankment against which waves may break, the cavities and orifices in said blocks on said higher portion also constituting from Q% to 60% of the total block volumes, and the cavities occupying the major part of the area of the upper portions of the blocks so that such layer thereof presents a cellular construction capable of destroying the formation of an advancing wave and of absorbing and storing such a substantial portion of the water thereof, that a major part of the water of the advancing wave is engulfed within such cavities and rendered unable to form a major reflection of such Wave, and the orifices in said blocks being of such size as to enable the engulfed water to pass through such blocks at a rate such that the engulfed water can flow into and down through said embankment so as to be substantially drained from the latter before a successive wave breaks on said structure, the total cross-sectional orifice area of l2 each block on said lower portion of the embankment being greater than the total cross-sectional orifice area of each block on said higher portion of the embankment.

6. A hydraulic structure for protection against the action of moving water and composed of a sloping embankment having a protective facing on the water side thereof, said embankment comprising a block supporting sloping layer of rocks of such sizes as to provide a void ratio above 20% and a permeability to the flow of Water such that water absorbed thereby from a Wave thereof is enabled to flow down therethrough at such rate that the absorbed water is substantially drained therefrom while such wave is receding and before a successive wave breaks on said structure, said facing comprising a plurality of blocks of large size and weight seated on the rocks of said sloping layer and forming on the latter a protective layer that is very permeable to the flow of water therethrough as compared with said sloping layer, said blocks being hollow box-shaped blocks having large cavities presenting large apertures to water impinging on the facing and extending down through the upper portions of the blocks to the bottom walls thereof and communicating at their lower ends with orifices extending through such bottom walls and enabling Water to pass from such cavities, through the bottom walls of the blocks and into the crevices between the rocks of said sloping layer, the total volume of the cavities and orifices in said blocks constituting from 20% to 60% of the total block volume so that said blocks are relatively light in weight for their size and unable by their own weight to withstand substantial hydrodynamic undenpressures exerted against their bottom walls by water flowing down through said sloping embankment layer, the total cross-sectional area of the large cavities in said blocks being substantially greater than the total orifice cross-sectional area in the bottom walls of such blocks, and at the tops of the blocks, constituting from 15% to 60% of the total area of the facing formed by such blocks, so that the upper portions of the blocks are substantially lighter than the lower portions thereof and present to an incoming wave of water a cellular construction capable of destroying the formation thereof and of absorbing such a substantial portion of the water of such wave that formation of a major reflection of such wave would be prevented, and the orifices in said blocks being sufiiciently large as to enable water caught in said cavities to drain quickly therefrom and before a successive wave breaks on said structure, and as to prevent the outward hydrodynamic thrust created in said sloping layer by the escaping water building up on the bottom walls of said blocks to a magnitude greater than the weight of the blocks.

7. A hydraulic structure such as defined in claim 6, in which the top of said embankment is mound-shaped and located substantially above the normal levels of the moving water, in which said sloping rock layer extends up onto the top of the embankment, and in which the upper portion of said protecting facing layer is seated on the rocks of said sloping layer at the top of the embankment, the blocks in such upper portion of said facing layer being formed to provide a larger Volume of cavities than the blocks on the lower portion of said facing layer, and having a total orifice cross-sectional area in the bottom walls thereof less than that of such lower blocks, whereby such upper blocks have a greater water containing capacity, but are less permeable than such lower blocks.

8. A hydraulic structure such as defined in claim 6, in which said embankment comprises a lower end portion abutting the lower end of said sloping rock layer and constituted of rocks of large size providing it with a permeability to water flow substantially greater than that of said sloping rock layer and providing an abutting shoulder forming a support for the bottom rows of blocks mounted on the lower end of said sloping layer, the blocks in said b tom rows having orifices of such cross-sectional area as to make them very permeable to water, and each having a total orifice cross-sectional area greater than the total orifice cross-sectional area of each block in the upper portion \of said facing layer.

9. A hydraulic structure such as defined in claim 6, in which the total cross-sectional orifice area at the lower end of the large cavity in said blocks is substantially less than the cross-sectional area of the lower end of such large cavity so that a shoulder is formed at the junction of such large cavity and an associated communicating orifice.

10. A hydraulic structure such as defined in claim 6, in which the total cross-sectional orifice area at the lower end of the large cavity in said blocks is substantially less than the cross-sectional area of the upper end of such large cavity, but substantially equal to the cross-sectional area of the lower end of such large cavity so that such large cavity and its associated communicating orifice are connected in a substantially continuous manner.

References Cited in the file of this patent UNITED STATES PATENTS 852,578 Rounds May 7, 1907 903,300 Marvick Nov. 10, 1908 905,596 Smith Dec. 1, 1908 929,728 Taylor Aug. 3, 1909 2,766,592 Danel et a1. Oct. 16, 1956 FOREIGN PATENTS 918,404 France Oct. 21, 1946 68,488 Netherlands Aug. 15, 1951 831,675 Germany Feb. 14, 1952 697,072 Great Britain 1953 763,795 Great Britain Dec. 19, 1956 

5. A HYDRAULIC STRUCTURE FOR PROTECTION AGAINST THE ACTION OF MOVING WATER AND COMPOSED OF A RUBBLE MOUND IN THE FORM OF A SLOPING EMBANKMENT AND A PROTECTING FACING PROVIDED ON SAID SLOPING EMBANKMENT, THE RUBBLE IN SAID EMBANKMENT BEING SUCH SIZES AND CONFIGURATIONS AS TO PROVIDE THE EMBANKMENT WITH SUCH PERMEABILITY THAT WATER ABSORBED THEREBY FROM A WAVE THEREOF IS ENABLED TO FLOW DOWN THERETHROUFH WHILE SUCH A WAVE IS RECEDING AND TO BE SUBSTANTIALLY DRAINED THEREFROM BEFORE A SUCCESSIVE WAVE BREAKS ON SAID STRUCTURE, SAID FACING COMPRISING A PLURALITY OF CONTAINER SHAPED BLOCKS LAID AS A LAYER ON THE LOWER PORTION OF THE EMBANKMENT AND DISPOSED GENERALLY IN SIDE-BY-SIDE RELATION WITH THE SIDE WALLS THEREOF IN SUPPORTING ENGAGEMENT AND THE TOP FACES THEREOF EXPOSED TO THE MOVEMENTS OF THE WATER, EACH OF SAID BLOCKS BEING RELATIVELY MASSINVE AND OF SUBSTANTIAL WIEGHT AND HAVING A LARGE CAVITY OPENING IN ITS TOP FACE AND AT LEAST ONE ORFICE IN ITS BOTTOM FACE BRINGING SUCH LARGE CAVITY INTO COMMUNICATION WITH THE PORTION OF THE EMBANKMENT ON WHICH IT RESTS, THE CAVITY AND ORFICE CONSTITUITING FROM 20% TO 60% OF THE TOTAL BLOCK VOLUME AND OCCUPYING SUCH A LARGE PORTION OF THE VOLUME OF THE BLOCK THAT THE BLOCK IS RELATIVELY LIGHT IN WEIGHT FOR ITS SIZE AND UNABLE BY ITS OWN WEIGHT TO WITHSTAND SUBSTANTIAL HYDRODYNAMIC UNDERPRESSURE EXERTED AGAIST ITS BOTTOM FACE BY WATER FLOWING THROUGH SAID EMBANKMENT, THE CAVITY IN EACH BLOCK OCCUPYING THE MAJOR PART OF THE AREA OF THE UPPER PORTION OF THE BLOCK, WHEREBY SAID LAYER OF SUCH BLOCKS PRESENTS TO AN INCOMING WAVE OF WATER A CELLULAR CONSTRUCTION WHICH IS CAPABLE OF DESTROYING THE FORMATION THEREOF AND OF ABSORBING AND STORING SUCH A SUBSTANTIAL PORTION OF THE WATER OF SUCH WAVE THAT FORMATION OF A MAJOR REFLECTION OF SUCH WAVE WOULD BE PREVENTED, AND AS THE ORFICES IN SAID BLOCKS BEING OF SUCH SIZE AS TO ENABLE WATER FLOWING DOWN FROM THE UPPER PORTION OF THE EMBANKMENT TO DRAIN OUT THROUGH SUCH ORIFICES AND CAVITIES AT SUCH RATE AS TO PREVENT THE BUILD UP OF HYDRODYNAMIC UNDERPRESSURE TO A MAGNITUDE SUFFICIENT TO DISPALCE SUCH BLOCKS ON THE EMBANKMENT AND SAID FACING COMPRISING A PLURALITY OF SAID CONTAINER SHAPED BLOCKS LAID GENERALLY AS A LAYER ON A HIGHER PORTION OF THE EMBANKMENT AGAINST WHICH WAVES MAY BREAK, THE CAVITIES AND ORFICES IN SAID BLOCKS ON SAID HIGHER PORTION ALSO CONSTITUTING FROM 20% TO 60% OF THE TOTAL BLOCK VOLUMES, AND THE CAVITIES OCCUPYING THE MAJOR PART OF THE AREA OF THE UPPER PORTIONS OF THE BLOCKS SO THAT SUCH LAYER THEREOF PRESENTS A CELLULAR CONSTRUCTION CAPABLE OF DESTROYING THE FORMATION OF AN ADVANCING WAVE AND OF ABSORBING AND STORING SUCH SUBSTNATIAL PORTION OF THE WATER THEREOF, THAT A MAJOR PART OF THE WATER OF THE ADVANCING WAVE IS ENGULFED WITHIN SUCH CAVITIES AND RENDERED UNABLE TO FORM A MAJOR REFLECTION OF SUCH WAVE, AND THE ORIFICES IN SAID BLOCKS BEING OF SUCH SIZE AS TO ENABLE THE ENGULFED WATER TO PASS THROUGH SUCH BLOCKS AT A RATE SUCH THAT THE ENGULFED WATER CAN FLOW INTO AND DOWN THROUGH SAID EMBANKMENT SO AS TO BE SUBSTANTIALLY DRAINED FROM THE LATTER BEFORE A SUCCESIVE WAVE BREAKS ON SAID STRUCTURE, THE TOTAL CROSS-SECTIONAL ORIFICE AREA OF EACH BLOCK ON SAID LOWER PORTION OF THE EMBANKMENT BEING GREATER THAN THE TOTAL CROSS-SECTIONAL ORIFICE AREA OF EACH BLOCK ON SAID HIGHER PORTION OF THE EMBANKMENT. 